An image forming apparatus of an electrophotographic method includes an optical scanning apparatus. The optical scanning apparatus emits a laser beam to a latent image bearing member such as a photosensitive drum to expose an image in the latent image bearing member.
In the image forming apparatus, there may be abnormally formed an electrostatic latent image in the latent image bearing member due to stray light caused from the optical scanning apparatus.
For example, the optical scanning apparatus includes an fθ lens and a polygon mirror. The stray light may be generated when the laser beam reflected on the polygon mirror is reflected on a lens holding frame which serves to hold the fθ lens. Specifically, the lens holding frame is integrally formed in a housing of the optical scanning apparatus. The housing serves as a mounting substrate of an optical component of an optical scanning apparatus 20. The lens holding frame is disposed to abut on both end surfaces in a longitudinal direction of the elongated fθ lens. The reflected light from the polygon mirror is incident on the end surface in the longitudinal direction of the fθ lens, the incident light is reflected on the end surface of the fθ lens and emitted therefrom, and the emitted light becomes the stray light and is emitted to the latent image bearing member.
As a countermeasure against the stray light, for example, in an incident surface of the fθ lens on which the reflected light from the polygon mirror is incident or an emitting surface, the housing is provided with a light-blocking wall which covers an area causing the stray light. Further, in the incident surface or the emitting surface, the housing is attached by a light-blocking sheet in the area causing the stray light.
On the other hand, in the automatic assembly of the optical scanning apparatus, there is a need to provide a jig to hold the fθ lens in order to position the fθ lens. However, in a case where the fθ lens is automatically assembled in the housing, the light-blocking wall provided in the housing interferes with the jig, so that it becomes difficult to dispose the light-blocking wall for preventing the stray light.